Systems and methods for monitoring physiology with unable-to-measure alerts

ABSTRACT

A system that observes and analyzes, and, only in the event of a significant negative condition, notifies and reports the event. In a hospital environment, the device includes a bedside unit connected to a pad or coverlet with a sensor array (placed under the patient) and also to an existing hospital nurse call system via an interface. The bedside unit is a wall-mounted unit with a display that becomes active when an alarm condition is enabled. Vigilance alarms are suspended if a patient is detected out of bed. An unable-to-measure alert is provided if the system is unable to reliably monitor. An alert message is generated and maintained on the display screen to inform a responding caregiver of the time and reason for any alarm. The system also may be adapted for use as a monitoring system for operators of motor vehicles, aircraft or other devices.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a division of, and claims priority to, U.S.application Ser. No. 14/252,748, filed Apr. 14, 2014, now U.S. Pat. No.9,275,533, which is a continuation of application Ser. No. 12/617,652,filed Nov. 12, 2009, now U.S. Pat. No. 8,698,635, which is a division ofU.S. application Ser. No. 11/624,207, filed Jan. 17, 2007, now U.S. Pat.No. 7,629,890, which is a continuation-in-part of U.S. application Ser.No. 11/004,589, filed Dec. 3, 2004, now U.S. Pat. No. 7,304,580, whichclaims the benefit of U.S. Provisional Application No. 60/526,612, filedDec. 4, 2003, the contents of which are incorporated herein by referencein their entirety.

This application incorporates by reference commonly owned U.S.application Ser. No. 09/662,006, now U.S. Pat. No. 6,984,207, and U.S.application Ser. No. 11/624,200, now U.S. Pat. No. 7,656,299, both intheir entirety.

FIELD OF THE INVENTION

The present invention relates generally to monitoring systems, and moreparticularly has reference to intelligent medical vigilance systems usedfor monitoring patients, automobile drivers, or other persons whosephysiological condition may undergo a change signifying a deteriorationin condition, a tendency toward drowsiness, or other state that may haveimportant consequences for that person or for others.

BACKGROUND OF THE INVENTION

Medical monitors have been in use for many years. Typically, medicalmonitors include patient monitors prescribed by a physician in a non-ICUsetting.

While typical devices may be suitable for the particular purpose towhich they address, they are not as suitable for providing an invisible“safety net” for a patient that will observe and analyze, and, only inthe event of a clinically significant negative condition, notify andreport the event to the care staff utilizing the hospital's existingnurse call system.

The main problem with conventional medical monitors is they are designedto respond to rapidly changing situations (found, in ICUs) and thus havea high false alarm rate. Outside the intensive care unit, these monitorsare not usually connected to a remote alarm, so local alarms sound,disturbing the patient, their family and friends and the workflow of thevarious clinicians providing care to the patient. Many attempts havebeen made to make alarms more meaningful.

Another problem is that standard devices require contact directly to thepatient's skin or body via cables or wires. This means constraining thepatient's movement to prevent disconnecting the sensors and also createsa danger of entanglement or strangulation from the cables. Additionally,these devices are relatively expensive to purchase and somewhat complexto operate, requiring a trained individual to operate properly.

Thus, a need exists for simpler, less expensive and more accuratemethods for noninvasive vital sign monitoring of significant negativeconditions and reporting these events. This invention addresses theseand other needs.

SUMMARY OF THE INVENTION

Briefly, and in general terms, the present invention involves a new andimproved intelligent medical vigilance system for providing an invisible“safety net” that observes and analyzes a person's vital signs. Only inthe event of a clinically significant negative condition will the devicenotify and report the event to the person or the care staff of a healthcare facility, utilizing, for example, a hospital's existing nurse callsystem. In so doing, the invention extends the vigilance capability and“reach” of the hospital clinical staff so that their resources can bemore effectively applied.

The present invention has many of the advantages of the medical monitorsmentioned heretofore and many novel features that result in a newintelligent medical vigilance system which is not anticipated, renderedobvious, suggested, or even implied by any of the prior art medicalmonitors, either alone or in any combination thereof.

In a presently preferred embodiment, by way of example and notnecessarily by way of limitation, the invention generally comprises abedside unit connected to a sensing array (placed under the patient) andto an existing hospital nurse call system via an interface. The sensingarray preferably is a non-invasive piezoelectric sensing film or othersimilar sensing technology, with an array of sensors installed in softpadding under the bottom sheet of the patient's hospital bed. Thesensing array is not directly in contact with the skin of the patient.Within the physical bedside unit are a signal processor and an alarmprocessor that measure the data and evaluate whether a clinicallysignificant event is occurring.

The bedside unit is a wall-mounted unit with a display that becomesactive (comes on) when an alarm condition is enabled or on command bythe nurse, by touching any key. It has a number of dedicated and softkeybuttons and controls for entering information, setting up specific itemsand interacting with the system.

The sensing array is a thin, piezoelectric film or other similar sensingtechnology, with an array of sensors sheathed in soft padding that iseasily cleaned. It is placed in the patient's bed, under the bottomsheet (and other padding if needed), not directly in contact with theskin of the patient. It can be integrated into the mattress coverlet, ifdesired. The monitoring system of the present invention may also be usedin chairs to monitor the state of relaxation of a subject via heartrate, blood pressure and respiration rates.

The nurse call feature is made up of hardware, software and cabling toconnect to a nurse call system already installed in the hospital or carefacility. The signal processor is made up of hardware and software thataccepts, buffers and converts the sensor array signal from analog todigital format for subsequent processing. The alarm processor uses logicto monitor the parameter trends and determines when a negative conditionis occurring. It then actuates the alarm circuitry for local and/orremote alarm. Soft alarms may be used to report adverse trends before anemergency condition arises. All alarms may interact with the existingnurse call system in the hospital.

In alternative embodiments, the intelligent medical vigilance system ofthe present invention can be adapted for use as a monitoring system foroperators of motor vehicles, aircraft or other devices. The presentinvention is installed in one or more of the following regions of amotor vehicle: the seat, seatback, headrest, steering wheel, drivingjacket, or a driving cap. One or more sensors may be located in eachgeneral location to provide for improved feedback. The vehicle operatormay also carry a wrist attachment or a necklace with built in sensors.

The sensors in the vehicle transmit information about the patient to acentral processor built into the vehicle via hardwiring or wirelesstechnology. The processor analyzes the incoming information and outputsdata as needed. The vigilance system can be used to alert drivers toapproaching sleep states or other potentially hazardous physicalconditions in order to reduce accidents. The sensors measure heart rate,respiration rate and movement of the vehicle operator.

Background noise signals are actively cancelled out to provide anaccurate reading of the patient's heart rate, respiration rate and bloodpressure. This cancellation allows the monitoring system to operateeffectively in high background noise environments.

Trend information is also recorded and available for study.

The present invention provides an intelligent medical vigilance systemthat overcomes many of the shortcomings of the prior art devices.

In a preferred embodiment, the present invention provides an intelligentmedical vigilance system for providing an invisible “safety net” for thepatient that will observe and analyze, and, only in the event of aclinically significant negative condition, notify and report the eventto the care staff utilizing the hospital's existing nurse call system.

In a further preferred embodiment, the invention provides an intelligentmedical vigilance system that observes (monitors) multiple physiologicalsignals without direct skin contact.

In yet a further embodiment, the invention provides an intelligentmedical vigilance system that analyzes the information to determinewhether the parameters are within normal limits or are tending to go ina clinically negative direction.

In a further aspect, the invention provides an intelligent medicalvigilance system that reports the physiological parameters and providesa trend of them over time.

In yet a further aspect, the invention provides an intelligent medicalvigilance system that notifies the nursing care staff when aconsistently negative situation is detected via the existing nurse callsystem used in the facility.

In still a further aspect, the invention provides an intelligent medicalvigilance system that persistently reminds nursing of continuedviolations or worsening situation until interventions are successful.This aspect provides an intelligent medical vigilance system thatextends the vigilance capability and “reach” of the busy clinical staffso they can spend time where it has the best clinical effect.

In another aspect, the invention provides a sensor system withinvehicles that alerts operators to dangerous physiological conditionsthat would impair the operator's ability to operate equipment safely.

These and other advantages of the invention will become more apparentfrom the following detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the vigilance monitoring system of the presentinvention.

FIG. 2 is a block diagram of the system functions.

FIG. 3 is a diagram showing progression from normal patient condition tonegative event and nurse response.

FIG. 4 is a time plot of multiple parameters, showing various parameterviolations and alarm logic.

FIG. 5 is multiple parameter alarm table, showing alarm logic.

FIG. 6 is a diagram showing various configurations of sensors in avehicle.

FIG. 7 is a flow diagram illustrating one embodiment of using a bed exitdetection system to enable and disable patient parameter alarms.

FIG. 8 is a flow diagram illustrating one embodiment of a system with anunable-to-measure alert capability.

FIG. 9 is a flow diagram illustrating one embodiment of an alarm pausefunction.

FIG. 10 is an enlarged illustration of a screen display for the displaydevice of FIG. 1, showing alert messages.

FIG. 11 is a table showing a set of alert message priorities.

FIG. 12 is an enlarged illustration of a latching alert message for thescreen display of FIG. 10.

FIGS. 13A and 13B are enlarged illustrations of non-latching alertmessages for the screen display of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an intelligent medical vigilance system 1, whichcomprises a bedside unit 3 connected to a sensing array 5 (placed underthe patient) and also to an existing hospital call system 7 via aninterface 9. Within the physical bedside unit 3 are a signal processorand an alarm processor that measure the data and evaluate whether aclinically significant event is occurring. The present invention canalso be used as a monitoring system in vehicles.

The bedside unit 3 is a wall-mounted unit with a display 9 that becomesactive (comes on) when an alarm condition is enabled or on command bythe nurse, by touching any key. It has a number of dedicated and softkeybuttons and controls for entering information, setting up specific itemsand interacting with the system.

While various types of sensors can be used, it is preferred that thesensing array 5 be in the form of a thin, piezoelectric film sensingarray sheathed in soft padding that is easily cleaned. It is placed inthe patient's bed 11, under the bottom sheet (and other padding ifneeded), not directly in contact with the skin of the patient. Thesensing array 5 may be incorporated into soft padding under the bottomsheet of a patient's bed.

The nurse call feature 7 is made up of hardware, software and cabling toconnect to the nurse call system already installed in the hospital orcare facility.

The signal processor is made up of hardware and software that accepts,buffers and converts the sensor array signal from analog to digitalformat for subsequent processing. Trend information is recorded andavailable for study.

The alarm processor uses logic to monitor the parameter trends anddetermines when a negative condition is occurring. It then actuates thealarm circuitry for local and/or remote alarm. Soft alarms may beutilized to report adverse trends before emergency situation arises.

FIG. 2 shows a schematic diagram of the monitoring process of thepresent invention. FIG. 3 is a diagram showing progression from normalpatient condition to negative event and nurse response.

In all patient monitoring devices with alarms the user can set “hard”alarm limits—those high and low single-parameter limits that, whenpassed, will cause the alarm indication, signal and tone to betransmitted to the caregiver by any number of means. The caregiverresponds to correct the situation. One problem caused by such alarms isthat of false positive alarms—those alarms that sound because the setthreshold is passed momentarily, but that are not associated with aclinically significant event. In order to monitor the patient closelythe alarm limits may be set close to the patient's present parametervalue. The closer these are set, the more likely it is that a minoractual parameter variation, patient movement or other signal “noise”will make the measured parameter surpass the set alarm limit.

Few if any alarms use any delay or additional processing other that thefiltering used to compute the average of and display the parameter'svalue. There have been many attempts to measure the inadequacy of suchsimple alarms in the intensive care unit. There are also methodologiesused to delay alarming until a certain time since passage outside therange integrated with the extent of the deviation beyond the set rangeis exceeded.

In an intelligent vigilance monitor such as the one used in thisinvention, the “hard” alarm limits can be spread more widely than inconventional intensive care unit monitors. This is done because thepatients being monitored may be relatively healthy and mobile comparedto typical ICU patients. Because of their high activity level theyexhibit a lot of variability in their measured vital parameters such asheart rate, respiratory rate, blood pressure, temperature, cardiacactivity, etc. Thus, the clinician wants to watch over these patients'condition, but also wants to avoid false positive alarms that disruptthe patient care workflow and the feelings and outlook of the patient.However, the clinician is still interested in detecting negative trendsin the patient so they can react quickly to treat or avoid deeper, moreserious problems.

FIGS. 4 and 5 show the use of alarm limit pairs and algorithms. FIG. 4is a time plot of multiple parameters, showing various parameterviolations and alarm logic. FIG. 5 is multiple parameter alarm table,showing alarm logic.

To accomplish a balanced response, the monitor of the present inventionhas two or more distinct alarm limit pairs and algorithms. The purposeof the new alarm scheme is to set new thresholds within the previous“hard” limits of each parameter that will catch a patient's worseningcondition prior to crossing the old single “hard” limits. This differsfrom just moving those limits in because these new, soft limits requirethat both the HR and RR values (in this example) be outside the softlimits to initiate the alarm. If either the HR or RR falls outside ahard limit, then the alarm sounds. If both the HR and RR fall outsidethe soft limit, but still within the hard limit, then the “soft” alarmsounds. This is best described in FIG. 4.

The parameters covered by such an alarm scheme are not limited to HeartRate and Respiratory Rate, used in this example. In factnon-parameter-based signals (noise, motion etc.) can also be included inthis logic scheme to make it more clinically valuable. In addition, thesensitivity and specificity of the “hard” alarm may be improved by usinga more-complex algorithm than just “did it pass the limit?” used in manysystems. This improvement could take the form of applying a number ofapproaches including but not limited to neural net and/or fuzzy logic.

Fuzzy logic could be applied to the limit as follows: Given one or moremeasurements of physiological parameters (e.g. heart rate, respirationrate, blood pressure, temperature, etc.) which require an alarm when themeasurement is outside of a range (or band), a fuzzy logic type functioncan be defined as follows:

${A = {\sum\limits_{n = 0}^{N - 1}{F_{n}\left( p_{n} \right)}}},$an alarm truth function, based on N different parameters or signals, anda signal truth function F(p) for each parameter or signal

${{F(p)} = \begin{Bmatrix}{1,{{{for}\mspace{14mu} p} < t_{L\; 1}}} \\{> {0\mspace{14mu}{for}\mspace{14mu} t_{L\; 1}} \leq p \leq t_{Lh}} \\{0,{{{for}\mspace{14mu} T_{Lh}} < p < t_{H\; 1}}} \\{{> 0},{{{for}\mspace{14mu} t_{H\; 1}} \leq p \leq t_{Hh}}} \\{1,{{{for}\mspace{14mu} p} > t_{Hh}}}\end{Bmatrix}},$with the additional constraint that F(p) must be monotonicallyincreasing for t_(Hl)<=p<=t_(Hh) and monotonically decreasing fort_(Ll)<=p<=t_(Lh).

The sum of N different physiological fuzzy logic functions can be usedto establish an alarm equation (See alarm truth function above)described further as follows: When A>=Ta, the alarm sounds, otherwise itdoes not. Ta is typically set to 0.5 if any weak (or soft) condition (orcombination of weak conditions) is to cause an alarm. If Ta is set to1.0 a strong alarm condition from at least one physiological parameteris required for the alarm to sound. If it is desired that the alarm onlysound when Physiological parameters are at or above t_(Hh)(n) (or belowt_(Ll)(n)), then Ta can be set to N. This method can also be used whenthe same physiological parameter is measured by multiple means.

In the case of two measurements of the same physiological parameter, theF(p) functions would most likely be the same for each measurement and Tacould be set to 1.0 such that if either device exceeded the t_(H)limits, the alarm would sound. The alarm violation type (hard, soft,etc.) may be differentiated from each other or not, depending on theneeds for the specific clinical application (ICU versus General CareFloor, etc.). The alarms may be set individually for each parameter assoft high and soft low or may be set by using a fixed percentage, suchas 10% within the range of the hard limits for each parameter. The logiccan also be extended to more than two alarms if needed.

The sensitivity of both the “hard” and “soft” limits also may beimproved by delaying the alarm until the monitor determines that asignal has passed a limit for a certain length of time, such as 10seconds. In this way, momentary changes in a signal having no clinicalsignificance can be ignored.

FIG. 6 is a diagram of the present invention installed in a vehicle. Theintelligent medical vigilance system of the present invention can easilybe adapted for use as a monitoring system for operators of motorvehicles, aircraft or other devices. The sensing array of the presentinvention is installed in one or more of the following regions of amotor vehicle: the seat 13, seatback 15, headrest 17, steering wheel 19,driving jacket 21, or a driving cap 23. One or more sensor arrays may belocated in each general location to provide for improved feedback. Thevehicle operator may also carry a wrist attachment 25 or a necklace 27with built in sensor arrays.

The sensor arrays in the vehicle transmit information about the patientto a central processor 29 built into the vehicle via hardwiring 31 orwireless 33 technologies. The processor analyzes the incominginformation and outputs data as needed. The vigilance system can be useto alert drivers to approaching sleep states or other potentiallyhazardous physical conditions in order to reduce accidents. The sensorscan be configured to measure a variety of parameters, such as heartrate, respiration rate, blood pressure, temperature, cardiac output andmovement of the vehicle operator. The intelligent monitoring system invehicles uses similar alarm schemes to those in a hospital setting.

Background noise signals are actively cancelled out to provide anaccurate reading of the operator's measured physiological parameters.This cancellation allows the monitoring system to operate effectively inhigh background noise environments.

There are various ways to enhance the reliability of the vigilancesystem, and make it even more useful as a tool for improving patientcare and clinical operations in a hospital, nursing home, assistedliving facility or other health care facility.

In one approach, a bed exit detection system can be integrated into thephysiological parameter monitoring system and used to ensure that thevigilance (parameter) alarms (alerts) will be discontinued once apatient leaves his bed and will remain suspended until the patientreturns to bed. In this way, the occurrence of a false alarm due to anempty bed, rather than an actual physiological condition of the patient,will be reduced.

Bed exit detection systems of various kinds are known. A bed exitdetection system continually monitors the presence or absence of apatient to determine whether the patient is in bed, is out of bed, or isattempting to exit the bed. These systems generally include some form ofsensing device attached to the bed, and a processor which is programmedto analyze signals from the sensor device to determine the patient's bedstatus and provide an alarm indication when out-of-bed, or often when anexiting-bed condition, is detected. A bed exit detection system which isespecially well suited for use with the present invention is describedin a commonly assigned, co-pending patent application entitled “Bed Exitand Patient Detection System” by Gentry, Glei, and Mills, filedconcurrently herewith, the full disclosure of which is incorporatedherein by reference. The system described in the co-pending applicationis especially well-suited because it provides both accurate in-bed andout-of-bed detection capabilities and because it can be easilyintegrated into a physiological monitoring system of the type describedherein.

The bed exit alarm is preferably made non-latching, i.e. if the patientexits the bed or tries to exit the bed the alarm will sound (if set),but if the patient responds to the alarm and gets back into bed, thealarm is silenced and reset. In some systems, the alarm includes apre-recorded voice message played in the vicinity of the patient's bedwarning the patient to return to the bed.

The bed exit system can be utilized with the physiological parametermonitoring system in at least two ways, as shown in FIG. 7. First, ifthere are no active vigilance alarms before the patient exits the bed ortries to exit the bed, the vigilance alarms are suspended until thepatient is detected back into bed. Once the patient leaves the bed, nonew vigilance alarms are generated.

On the other hand, if a vigilance alarm is active before the patientleaves the bed or tries to leave the bed, those alarms are continuedeven after the patient leaves the bed. The alarms are continued toinform the nurse or clinical staff of the patient's condition before thebed exit event occurred.

In the present invention, the bed exit detection system can beintegrated with the physiological parameter monitoring system in severaldifferent ways, but in at least one approach, the patient parametersensors and the bed exit sensors are mounted in a common sensing array5, and both the bed exit detection function and the physiologicalmonitoring function are carried out by the same processors, which areprogrammed to disable the vigilance alarms when an out-of-bed or anexiting-bed condition is detected, and to enable the vigilance alarmswhen an in-bed condition is detected. In most cases, it is desirable tocontinue physiological monitoring and data collection even when thevigilance alarms are disabled, so that the data may be stored in memoryfor future review and analysis, as needed. In addition, in most cases,the arming and disarming of the vigilance alarms will continue, even ifthe bed exit alarm is turned off, as for example, in the case of apatient who is not on bed exit restrictions.

It will be appreciated that a bed exit detection system can beintegrated with any type of physiological parameter monitoring system inthe manner described, and that the invention is not limited to theparticular parameter monitoring and alarm system described herein.

In some embodiments, it also may be desirable to alert the nurse orother caregiver that the system is unable to reliably monitor thepatient due the presence of certain extenuating conditions. Theconditions which might result in an unable-to-measure (UTM) situationare generally predetermined, and can differ from system to system.Examples of typical UTM conditions might include (1) excessive patientmotion such as that caused by seizures, physical or chest therapy, orthe application of certain devices that may cause severe motion (largeenough to cause the sensor signal-to-noise ratio to fall below apredetermined threshold); (2) low or no signal from the physiologicalsensors (e.g. sensor signal falls below the noise threshold of thesystem or below a predetermined amplitude threshold); (3) a foreignobject (e.g. a heavy suitcase) being placed on the bed surface(resulting in an in-bed determination by the bed exit detection system,but no physical signal from the physiological parameter sensors); (4) a“Select Patient” prompt not being answered by the clinician duringinitial set up of the system to start monitoring for a new patient; (5)sensor disconnection or sensor failure; (6) heart rate (HR) above orbelow operational limits of the system (for example, 35-200 beats perminute); or (7) respiration rate (RR) above operational limits of thesystem (for example, 70 breaths per minute). If any of these conditionspersist for a prescribed delay period (e.g. two minutes or more), analarm will be generated to bring someone to the patient's bedside. A twominute threshold for the delay time provides a balance between speed ofresponse and the occurrence of false alarms. A shorter delay timethreshold would provide a faster response but a higher probability offalse alarms. A longer delay time threshold, on the other hand, wouldreduce the occurrence of false alarms but might not provide enough timefor a response team or nurse to administer treatment to a patientundergoing seizures or to otherwise resolve in a timely fashion thecondition which caused the UTM alert.

In some embodiments, as shown for example in FIG. 8, a UTM conditioninitially is reported as a low level notification to the caregiver onthe display screen 9 when the condition is first detected by theprocessor, then escalated to a full UTM alert if the condition persistsfor the preset delay time, in order to notify the caregiver that apatient is not being monitored. A typical UTM indication on the displayscreen 9 would include a dash/dash (--) display for heart rate andrespiration rate. While the UTM condition is non-latching (low levelnotification is non-latching), the escalated UTM alert is a latchingalert. In other words, if the UTM condition persists for less than thedelay period (e.g., two minutes) and then resolves itself, the low levelnotification is removed from the screen and no UTM alert is initiated.However, once the full UTM alert is triggered after the delay period, itwill continue, even if the UTM condition resolves itself.

Another approach for improving the vigilance system, involves providingan Alarm Pause function as shown in FIG. 9, which causes both theparameter alarms and the bed exit alarms to be paused for a period oftime (such as, for example, five minutes). In the case of the parameteralarms, the alarm pause function will temporary silence any audiblealarm and reset the nurse call relay to its normal state to give theresponding caregiver time to investigate and resolve the situationcausing the alarm. In at least one embodiment, the alarm pause functionis actuated by a push button which starts a timer counting down from thepreset delay time (e.g., 300 seconds) and automatically re-enables thealarm once the alarm pause period times out. If the condition causingthe alarm remains in effect, the alarm signal is re-initiated. If theresponding caregiver wishes to re-enable the alarm before the alarmpause function has timed out, they can press the alarm pause buttonagain and the alarm will be re-enabled. On the other hand, if they pressthe alarm pause button a third time, i.e. after the alarms arere-enabled, they will place the unit into alarm pause mode again foranother preset period of time.

In the case of the bed exit alarms, the alarm pause button is typicallypressed when the nurse or other caregiver wants to remove a bedrestricted patient from the bed or to perform some procedure which mayinterfere with bed exit monitoring. The reason for the bed exit alarm isto alert the nurse or caregiver to abnormal conditions. Thus, if thepatient is being assisted by the nurse, there is no reason to initiateor continue a bed exit alarm. Instead of asking the caregiver to changethe bed exit restriction setting (on/off) every time the patient ishelped out of the bed for bathroom visits and the like, the alarm pausefunction is used to provide a form of supervised bed exit. Supervisedbed exit is activated if the patient leaves the bed when alarm pause isactive or if alarm pause is pressed after the patient has left the bed.With supervised bed exit, the nurse or caregiver can suspend the bedexit alarm when the patient leaves the bed with assistance, andautomatically re-enable the bed exit alarm once the patient returns tothe bed.

In most cases, the alarm pause function is provided by themicroprocessor in the bedside unit 3 which is programmed to sense theinput signals from the sensing array 5 and, in response and inaccordance with its programming instructions, to generate an outputsignal for activating the alarms. In at least one embodiment, theprocessor is configured to receive user instructions via an externalsignal from a push button 12 mounted on the face of the bedside unithousing. By pressing the button 12, the caregiver instructs the programto enter into the alarm pause mode, causing the processor to discontinueany current alarms and to wait for the preset period of time beforegenerating an output signal to the alarm circuit or the nurse callsystem 7. Pressing the button a second time instructs the processor tooverride the time delay.

In addition to reporting the occurrence of a clinically significantnegative condition to the care staff by sending an alarm signal over thenurse call system 7 and/or by generating a local alarm at the bedsideunit 3, in at least some embodiments, the system also is configured todisplay an alert message on the bedside unit display screen 9 informingthe caregiver of the type of alert, the values that triggered the alert,and the time the alert was raised. In this way, a caregiver respondingto an alarm over the nurse call system will be informed immediately uponentering the patient's room why and when the alarm was raised, so thathe or she can begin to immediately resolve the problem or situation.

The alert messaging system can be configured in a variety of differentways, but in at least one embodiment, the alert messaging system isconfigured to display at least four messages in a priority-based queuewith the four highest priority messages being displayed at any giventime. The messages can be further divided into two types, latching alertmessages and non-latching alert messages. A latching alert is one thatremains in an alarm condition once the alarm signal is initiated untilstopped by a deliberate action on the part of a responder. A singlequeue is provided for both latching and non-latching messages, with amaximum of four messages being displayed at any time. If the queue islonger than four, there will be queued messages that are not currentlyon display.

A latching alert message typically accompanies latching physiologicalalarms. Thus, for example, the heart rate and respiration rate valuesthat caused the alarms and the time at which the alarms was raised arepart of the message. The messages are cleared only when the alarm iscleared or reset. Clearing a latching alert message requires userintervention. If multiple latching alarms of the same type occur whilean alarm is active, the message accompanying the first instance of thealarm will continue to be displayed.

One of the benefits of a latching alert message is that it provides theresponding caregiver with an immediate indication of the reasons for analarm regardless of how long ago the alarm event occurred. Traditionalmonitors typically display information concerning the current state ofthe patient, which might return to normal by the time a caregiverresponds to an alarm. In such cases, the caregiver will not immediatelyknow the reason for the alarm, and might mistakenly believe that a falsealarm has occurred. By providing a latching alert message in accordancewith the present invention, the caregiver is immediately informed of thereason for the alarm as soon as they reach the patient's bedside.

Non-latching alert messages typically accompany non-latching bed exitalerts (in systems equipped with a bed exit detection capability). Thetype of alert and the time at which the alert was raised are part of themessage. The message is cleared only when the alert is cleared. Thus, ifthe condition that caused the alert is resolved (such as by the patientreturning to bed), the alert is reset. However, the alert messagecontinues to be displayed even if the alert is reset until userintervention. If multiple alerts of the same type occur, then multiplemessages are generated and displayed according to the assignedpriorities.

FIG. 10 is an example of a typical screen display produced by thebedside unit 3 on the display monitor 9. A message box area 14 isprovided between a parameter display area 16 at the top of the screen(containing numeric windows 18 for heart rate and respiration rate) anda trend and waveform area 20 at the bottom of the screen (containingwaveform and trend displays for the heart rate and respiratory ratedata). The message box window 14 is used to display the alert messagesto the caregiver. In the embodiment shown, three alert messages aredisplayed simultaneously. The first message shows that a heart rate of140 bPM (exceeding the upper heart rate limit of 135 bPM for thatpatient) occurred at 8:36 P.M. The second message shows that arespiration rate of 12 BPM (below the 13 BPM lower limit for thepatient) occurred at 8:37 P.M. The third message shows that a soft limitHR/RR warning also occurred at 8:37 P.M. All three messages aredisplayed simultaneously in priority order.

In the embodiment shown, up to four short messages can be displayed inthe message box 14 to indicate the reason for any alarm, or to provideother alert message. It will be appreciated, however, that the size,location and/or capacity of the message box can be varied, if desired.When an alert message comes up, a beep tone typically will sound fromthe bedside unit 3 to signal the caregiver that there is a new message.The message is cleared by the caregiver by pressing the alarm pausebutton 12.

While various different priority assignments can be made, a typical setof priority assignments for use with the present invention is shown inFIG. 11. In this example, the bed exit alerts are given the highestpriority, followed by the heart rate (hard limits), respiration rate(hard limits), unable-to-measure (UTM), and HR/RR warnings (softlimits), in that order. The remaining (lower) priorities in this exampleare assigned to various mechanical failures and system malfunctions. Itwill be appreciated that fewer or more priority items can be used, andthat the order of priorities rearranged, if desired.

The operation of the latching alert messages can be best understood byreference to FIG. 12. Assume, for example, a patient with a heart rate(HR) hard limit of 130 bPM (upper) and 40 bPM (lower). If the patient'sheart rate rises to 140 bPM at 8:01 A.M., an alert is raised. The nursecall light is turned on, and the display screen on the bedside unitdisplays an alert message 22 of the type shown in FIG. 12. If thepatient's heart rate falls to 110 bPM at 8:02 A.M., the nurse call lightremains on, and the same alarm message 22 remains on the screen. If thepatient's heart rate rises to 150 bPM at 8:03 A.M., the nurse call lightcontinues to be on and a new alert is raised, but the same alert message22 remains on the display screen, as shown in FIG. 12. The alert messageremains unchanged because the new alert is of the same type (i.e. HRhard limit) as the initial alert, and in such cases, the initial alertmessage remains on the display 9. If the patient's heart ratesubsequently falls to 110 bPM at 8:06 A.M., the alert message 22 on thedisplay 9 will continue to remain unchanged, until the nurse visits thepatient's room and presses the alarm pause button 12 or otherwise resetsthe system. Pressing the alarm pause button turns off the nurse calllight and clears the alert message from the screen. Thus, it will beappreciated, that a latching alert message remains on the screen untilboth the alert condition goes away and the alarm pause button 12 ispressed (or the system is reset by the caregiver in some other fashion).

Operation of the non-latching alert messages is best understood byreference to FIGS. 13A and 13B. Assume a patient on bed exitrestrictions with the bed exit alarm system turned on. If the patientleaves or tries to leave the bed at 8:01 A.M., a bed exit alert israised, the nurse call light is turned on, and an alert message 24 isdisplayed on the screen 9 of the type shown in FIG. 13A. If the patientreturns to bed at 8:02 A.M., the bed exit alert is discontinued, thenurse call light is turned off, but the message 24 remains on the screen9. If the patient leaves the bed again at 8:03 A.M., the nurse calllight is once again turned on, and the alert message 26 now reports bothalarm occurrences in chronological sequence from top (most recent) tobottom (less recent), as shown in FIG. 13B. Both alert messages willremain on the screen until the alarm pause button 12 is pressed or thesystem is otherwise reset by the caregiver.

While particular forms of the invention have been illustrated anddescribed, it will also be apparent to those skilled in the art thatvarious modifications can be made without departing from the spirit andscope of the invention. Accordingly, it is not intended that theinvention be limited except by the appended claims.

We claim:
 1. A method for improving the reliability of a system formonitoring physiology of a person, comprising: placing adjacent theperson a plurality of sensors configured to detect physiologicalparameters of the person; detecting one or more physiological parametersof the person with said sensors; converting the detected parameters tosignals; assigning one or more alert conditions; analyzing the signalsto determine if they satisfy at least one of the alert conditions;activating an alert when at least one of the signals satisfies an alertcondition; assigning one or more unable-to-measure conditions whichindicate that at least some of the signals are unreliable; analyzing thesignals to determine if they satisfy at least one of theunable-to-measure conditions; and providing an unable-to-measure alertwhen at least one of the unable-to-measure conditions is satisfied. 2.The method of claim 1, wherein the unable-to-measure conditions areselected from a group consisting of excessive motion by the person, lowsignal amplitude, low signal-to-noise ratio, sensor disconnection,sensor failure, and patient parameters outside operational limit.
 3. Themethod of claim 2, further comprising: placing a plurality of sensors ona bed to detect a presence thereon of a person or a foreign object;detecting or more signals from said sensors on the bed; and analyzingthe signals to determine whether a person or foreign object is in thebed; wherein the unable-to-measure conditions further comprise thepresence of an in-bed determination with the absence of a signal fromthe sensors configured to detect physiological parameters.
 4. The methodof claim 3, further comprising; activating a bed exit alert when thesignals from the sensors on the bed indicate that the person is out ofbed; and disabling the bed exit alert when the person is removed fromthe bed under supervision.
 5. The method of claim 1, wherein theunable-to-measure alert is provided only when the at least oneunable-to-measure condition persists for a predetermined minimum periodof time.
 6. The method of claim 5, wherein the unable-to-measure alertcomprises an alarm.
 7. The method of claim 5, wherein a low levelnotification is provided when the at least one unable-to-measurecondition persists for less than the predetermined minimum period oftime.
 8. The method of claim 7, wherein the low level notificationcomprises a sequence of dashes on a display screen.
 9. The method ofclaim 5, wherein the unable-to-measure alert is a latching alert. 10.The method of claim 7, wherein the low level notification isnon-latching.
 11. The method of claim 1, wherein the unable-to-measurealert comprises a sequence of dashes on a display screen.
 12. Theapparatus of claim 1, wherein the sensors are configured to detectphysiological parameters of the period without direct contact with theperson.
 13. Apparatus for monitoring physiology of a person, comprising:one or more physiological sensors configured to detect physiologicalparameters of a person and generate corresponding electrical signals; aprocessor configured to analyze the signals from the sensors todetermine if the physiological parameters of the person satisfy at leastone alert condition; and an alert system in communication with theprocessor for providing an alert when at least one of the physiologicalparameters satisfies an alert condition; the alert system being furtherconfigured to provide an unable-to-measure alert when the processordetermines that the signals satisfy an unable-to-measure condition whichindicates that at least some of the signals are unreliable.
 14. Theapparatus of claim 13, wherein the unable-to-measure alert is providedonly when the processor determines that the unable-to-measure conditionhas persisted for a predetermined minimum period of time.
 15. Theapparatus of claim 13, wherein the unable-to-measure alert comprises analarm.
 16. The apparatus of claim 15, wherein the alarm is provided overa nurse call system.
 17. The apparatus of claim 13, wherein thephysiological sensors comprise piezoelectric films.
 18. The apparatus ofclaim 13, wherein the unable-to-measure alert is provided on a displayin a bedside unit.
 19. The apparatus of claim 13, wherein a low levelnotification is provided when the unable-to-measure condition persistsfor less than the predetermined minimum period of time.
 20. Theapparatus of claim 13, further comprising a display in communicationwith the processor, wherein the unable-to-measure alert comprises avisual indication on the display.
 21. The apparatus of claim 19, furthercomprising a display screen in communication with the processor, andwherein the low level notification comprises a sequence of dashes on thedisplay screen.
 22. The apparatus of claim 13, wherein theunable-to-measure alert is a latching alert.
 23. The apparatus of claim19, wherein the low level notification is non-latching.
 24. Theapparatus of claim 13, wherein the physiological sensors are configuredfor installation in a motor vehicle to determine the physiology of aperson operating the vehicle.
 25. The apparatus of claim 24, wherein thephysiological sensors are installed in a seat, seatback, headrest orsteering wheel in the motor vehicle.
 26. The apparatus of claim 25,wherein the processor is installed in the motor vehicle, and thephysiological sensors are connected to the processor via hardwiring totransit the signals from the sensors to the processor.
 27. The apparatusof claim 25, wherein the processor is installed in the motor vehicle,and the physiological sensors are wirelessly connected to the processorto transmit the signals from the sensors to the processor.
 28. Theapparatus of claim 24, wherein the alert system alerts the personoperating the vehicle to an approaching sleep state or other potentiallyhazardous physiological condition.
 29. The apparatus of claim 24,wherein the physiological sensors are configured to determine movementof the person operating the vehicle.
 30. The apparatus of claim 13,wherein the physiological sensors are configured for installation in achair to determine the physiology of a person sitting in the chair. 31.The apparatus of claim 13, wherein the physiological sensors areconfigured for installation in a chair to monitor the state ofrelaxation of a person sitting in the chair.
 32. The apparatus of claim13, wherein the physiological sensors are configured for installation inan aircraft for monitoring the physiology of a person operating theaircraft.